As the secondary battery that can charge and hold electricity therein, a lead-acid storage battery, a nickel-cadmium storage battery, a lithium-ion secondary battery and so on have been developed and practically used. Recently, an all-solid secondary battery which can be formed of a thin film is attracting attention and is progressively applied to smaller devices because of its safety and reduction in packaging space.
In Non-Patent Document 1, a secondary battery is mounted in a small device that measures the intraocular pressure being the cause of glaucoma or the like that is a disorder of the eye. To measure the pressure with the small device inserted in the eye, a thin film lithium-ion battery is mounted which can be downsized. FIG. 18 is an IOPM (Intraocular Pressure Monitor) disclosed in Non-Patent Document 1. The IOPM is a device of a micro-size to be inserted into the eyeball, and the thin film lithium-ion secondary battery is used as an integral type power supply. A thin film lithium-ion secondary battery 102 is mounted on the top of a pressure sensor 100, and a microprocessor for control, a circuit part 104 such as a storage element and so on are further mounted. The pressure sensor 10, the thin film lithium-ion secondary battery 102, and the circuit part are made by physically superposing individual discrete components.
In Non-Patent Document 2, a compact sensor has been developed which is used for environmental monitoring and biological monitoring in the medical field and requires no charge or battery change as illustrated in FIG. 19. Sensor units operating for a long period by suppressing power consumption have been conventionally published, but could not be downsized as the whole of the sensor unit because a small size battery is insufficient in power capacity and therefore the size of the battery is an obstacle. Therefore, the power-saving technology has been introduced into the control of the microprocessor and the sensor, and the solar battery and the lithium-ion battery built therein have been downsized by thinning them, thereby developing a compact sensor unit operating for a long period. The external appearance of the sensor unit has a size of 3.5 mm×2.5 mm×1.0 mm and a volume of 8.75 mm3. At the top, four solar battery cells 124 are provided and have a total area of 2 mm2. Under the solar battery cells 134, a 32-bit microprocessor 132, a memory, and a thin film lithium-ion secondary battery 130 are stored. The volume of the thin film lithium-ion secondary battery is extremely small such as 2.9 mm3.
The thin film lithium-ion secondary battery 120 embedded in the compact sensor is made by fabricating a plurality of chips on a silicon wafer and cutting them into individual chips. The chip is attached to a tape as it is or packaged for packaging, and packaged on and soldered to a circuit board by a packaging device. The secondary battery which has been made into a chip as described above can be handled as one component.
Patent-Document 1 discloses a semiconductor device in which a solid thin film secondary battery is monolithically embedded by forming the solid thin film secondary battery on a substrate, and a semiconductor device in which an electronic element and the solid thin film secondary battery are monolithically configured in a circuit. The solid thin film secondary battery is an all-solid lithium-ion secondary battery, and is monolithically embedded by forming the solid thin film secondary battery which uses a porous film formed by surface modification of a semiconductor substrate as an anode active material, on the substrate.
As illustrated in FIG. 20, in an IC/LSI chip 116 on a monolithic secondary battery embedded semiconductor substrate, the monolithically formed solid thin film secondary battery is connected to an IC/LSI part by internal connections 112-1, 112-2. On the substrate of the IC/LSI chip 116, a monolithic solid thin film secondary battery group 110-1 for supplying power to a memory circuit part 114 and a monolithic secondary battery group 110-2 for supplying power mainly to a logic circuit part 113 are integrated together with the circuit group. Both of them can be electrically connected by a plurality of respective internal connections. They can also be externally connected, in which case, however, the advantage of the monolithic method is considered to be greatly lost.
Patent Document 2 also discloses a semiconductor element substrate on which the all-solid lithium-ion secondary battery is mounted as the solid battery.
Patent Document 3 discloses a battery-mounted type integrated circuit device in which a semiconductor chip is mounted on a solid battery. The solid battery has a charge element including a cathode, an anode and a solid electrolyte material, and a protective film outside the charge element, in which the protective film is configured in a multilayer structure and at least one layer thereof has a positive potential. Use of the protective film makes it possible to prevent diffusion ions performing charge and discharge, into the integrated circuit so as to inhibit deterioration of characteristics and malfunction of the semiconductor device and thereby take the semiconductor device into a package, so that a battery mounted-type integrated circuit device with reduced packaging area can be provided.
As illustrated in FIG. 21, a silver paste is applied onto a lead frame 120 fabricated for mounting a battery, and a solid battery 122 is heated at 200° C. and placed. A liquid epoxy resin is applied thereon, and a semiconductor chip 124 is placed. The semiconductor chip and the lead frame, and the solid battery 122 and the lead frame 128 are soldered and wired by an insulation-coated gold wire having a diameter of 100 μm, and an epoxy resin 126 is used to seal them.